The overall objective of this research is to develop antibody fusion proteins for the targeting of cytokines and/or co-stimulatory molecules to tumors expressing carcinoembryonic antigen (CEA) for immunotherapy. These studies will use a high affinity anti-CEA Mab, T84.66, for genetically engineering fusion proteins that will be studied in a CEA transgenic mouse model. In the first aim, anti-CEA fusion proteins will be constructed that contain IL-2, IL-12, IL-18, GM-CSF, CD40L, or FIt3L. Single gene-encoded or multi-chain fusion proteins will be produced and characterized for their stability, molecular size, and functional properties. Antigen binding properties will be examined by enzyme immunoassay, reaction with cell surface antigen, and surface plasmon reasonance. The biological activity of fusion proteins will be determined in proliferation, IFN-gamma production, and effector cell retargeting assays. For the second aim, the pharmacokinetics, normal tissue distribution, and tumor targeting properties of radioiodinated fusion proteins will be studied. Tumor localization will be determined in CEA transgenic mice bearing CEA-expressing marine colon carcinomas. Antibody accumulation in CEA-negative parental tumors growing in the same animal will measure the specificity of tumor targeting. In the final aim, the therapeutic properties of fusion proteins alone or in selected combinations will be studied in CEA transgenic mice bearing tumors with low immunogenicity. The therapeutic benefit derived from co-administration of fusion proteins that act synergistically or have different immune cell targets will be examined. Mechanisms of tumor rejection will be investigated in mice following ablation of lymphoid populations or in immunodeprived animals. Recombinant antibody fusion proteins that are targeted to CEA- expressing tumors and have the capacity to induce and augment antitumor responses will provide the opportunity for more effective immunotherapy of human carcinomas.